48 lines
1.6 KiB
Haskell
48 lines
1.6 KiB
Haskell
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-- | Interval-based implementation of preview polling
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{-# LANGUAGE CPP #-}
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module Hakyll.Preview.Poll
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( previewPoll
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) where
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--------------------------------------------------------------------------------
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import Control.Applicative ((<$>))
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import Control.Concurrent (threadDelay)
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import Control.Monad (filterM)
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#if MIN_VERSION_directory(1,2,0)
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import Data.Time (getCurrentTime)
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#else
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import System.Time (getClockTime)
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#endif
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import System.Directory (doesFileExist, getModificationTime)
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--------------------------------------------------------------------------------
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import Hakyll.Core.Configuration
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--------------------------------------------------------------------------------
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-- | A preview thread that periodically recompiles the site.
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previewPoll :: Configuration -- ^ Configuration
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-> IO [FilePath] -- ^ Updating action
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-> IO () -- ^ Can block forever
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previewPoll _ update = do
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#if MIN_VERSION_directory(1,2,0)
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time <- getCurrentTime
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#else
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time <- getClockTime
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#endif
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loop time =<< update
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where
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delay = 1000000
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loop time files = do
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threadDelay delay
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files' <- filterM doesFileExist files
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filesTime <- case files' of
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[] -> return time
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_ -> maximum <$> mapM getModificationTime files'
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if filesTime > time || files' /= files
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then loop filesTime =<< update
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else loop time files'
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